Electrochemical Exfoliation of the Two-Dimensional Conjugated Metal–Organic Framework for High-Performance Urea Electrooxidation

Two-dimensional (2D) conjugated metal-organic frameworks (c-MOFs) have attracted extensive interest in electrochemical fields due to their inherent electrical conductivity. However, the severe interlayer stacking still poses barriers toward their potential applications. The reliable synthesis of ultrathin c-MOF nanosheets is crucial yet remains challenging. Herein, we demonstrate an electrochemical exfoliation approach to obtain ultrathin nanosheets from layer-stacked c-MOF crystals. Our results reveal the electric field-induced ion intercalation mechanism and provide a viable method for the synthesis of ultrathin M-HHTP (M = Ni, Cu, Co; HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanosheets. To prove utility, the obtained Ni-HHTP nanosheets as urea oxidation reaction (UOR) catalysts achieve an ultrahigh current density of 165.7 mA cm-2 at 1.35 V versus a reversible hydrogen electrode and nearly 100% selectivity of N-products. Experimental characterization and theoretical calculations reveal that the fully exposed square planar NiO4 active centers effectively reduce the energy barrier of C-N bond cleavage for UOR and suppress the parasitic oxygen evolution reaction.